Under former manager Carlo Ancelotti, Milan were the dominant team on the European stage from 2001 to 2007 – reaching the semi-finals twice, the final thrice and winning two out of those three finals (the remaining match being Liverpool’s famous comeback in Istanbul).

Barcelona, led by Pep Guardiola, then took over the mantle as kings of Europe, reaching two semi-finals and two finals, winning both against Manchester United, all in the space of four years.

Milan were missing a raft of players through injury, the most high-profile casualty being their No.1 centre-back Thiago Silva, ruled out for a month. Their injury woes have been well-covered, and following their near-collapse at Arsenal in the last round, many had written off Massimiliano Allegri’s side.

Thiago Silva was ruled out for a month

Ageing but world-class centre-back Alessandro Nesta played alongside Phillipe Mexes, with Daniele Bonera at right-back and Luca Antonini at left-back. Mark Van Bommel was injured so captain Massimo Ambrosini played the anchorman role, with veteran Clarence Seedorf on his left and tireless midfielder Antonio Nocerino on his right.

Robinho, supposedly the striker who brings the best out of talisman Zlatan Ibrahimovic, started in attack alongside the big Swede. Kevin Prince Boateng, Milan’s vital link between defence and attack, was also in the starting XI having just recovered from injury, playing at the tip of the midfield in a 4-1-2-1-2/4-3-1-2 formation.

Barcelona’s personnel were as expected, although Guardiola set his up in a rough 3-4-3/4-3-3 formation. Captain Carles Puyol shifted to left-back after Eric Abidal’s coming operation, leaving Javier Mascherano partnering Gerard Pique at centre-back.

Dani Alves played on the right-side (more on that later), Sedyou Keita sat alongside Sergio Busquets at the base of midfield with Xavi ahead of them. Up front, Alexis Sanchez on the right and Andres Iniesta on the left flanked the free-roaming Lionel Messi.

A crowded midfield

Barcelona’s formation was a fluid one based whether or not they had the ball: they played a 3-4-3 when they had possession – Alves pushing up so high that he was often playing as a right-midfielder/winger, with Puyol coming across to form a back 3 – and then shifted back to a 4-3-3 when they lost the ball, with Alves shuttling back to his right-back position.

Being a student of Cruyff, Guardiola’s decision to play a 3-4-3 made tactical sense as Barcelona were guaranteed an extra man at the back: 3 centre-backs versus Milan’s 2 strikers, with Busquets and Keita taking turns to track Boateng.

As a consequence of playing both Busquets and Keita, two primarily defensive-minded midfielders, Xavi was pushed up to being the apex of Barcelona’s midfield diamond. Xavi’s best position is central midfield, where he collects the ball from deep before pinging the ball forwards to his more advanced teammates. As the furthest midfielder forward, he often played with his back towards goal, and had less passing options than he usually has. His natural technical abilities helped him perform adequately, but it was far from his ideal role.

Like a domino effect, Iniesta was also pushed further forward as part of a front three, when he prefers to play just ahead of Xavi as the most advanced midfielder. Iniesta’s discomfort with his role in this game was visibly obvious, being subbed off on the 65th minute after taking 3 shots, all of which were off-target, in a personally very quiet game.

During those 65 minutes, Iniesta stayed out wide on the left, but upon receiving the ball, passed it back into the centre and then moving himself into the centre as well. On the other side, despite Sanchez making his name as a right-sided winger for Udinese, he didn’t even attempt to provide width, often almost playing as a striker alongside Messi. This resulted in an incredibly narrow Barcelona side, with the only true width coming in the form of the enthusiastic Alves. He was an outlet that Barcelona couldn’t take full advantage of, apart from having a goal rightly ruled out when Alves passed to an offside Messi.

Barcelona’s chances that came from playing through the middle were often just half-chances rather than clear cut goalscoring opportunities. Messi had a shot from the middle which Abbiati spilled, but Alves failed to convert on follow up.

There was a huge shout for a Barcelona penalty in the 15th minute as well, which probably should have been given when Abbiati felled Sanchez (although Sanchez was also probably looking for it), but that chance came from a clever free-kick routine rather than any tactical play.

Abbiati brings down Sanchez but referee rules no penalty

There was one half-chance for Barcelona from the middle, when Xavi advanced forward, skipped past two half-hearted challenges from Robinho and Boateng, played a one-two with Messi before firing a low shot which Abbiati palmed away. Still, Xavi’s shot came when he was in the penalty box, and although he had clear sight of goal and should’ve done better, he wasn’t past Milan’s rearguard; Barcelona hardly got clear of Milan’s defence.

Another Barcelona centralised-chance came from Iniesta’s one good moment as he swiftly exchanged passes with Xavi, played a through-ball to Sanchez who cleverly flicked the ball to an unmarked Xavi. Unfortunately for Barcelona, Xavi’s shot was deflected of the ever-alert Nesta and into Abbiati’s hands.

The one time Barcelona got behind Milan’s defence was from a counterattack, but as Sanchez raced onto Keita’s header and looked to be clear on goal, Antonini intervened to make a stunning last-gasp, sliding tackle.

Even though the likes of Messi and Sanchez are more than capable of playing in wider roles, it seemed like Guardiola had instructed them to stick to their central positions.

It was a baffling tactical decision, not only because adding width would undoubtedly stretch Milan’s backline who were missing two first-team regulars in Ignazio Abate and Silva, but also because Milan are extremely weak defending their wide areas. Tottenham’s Aaron Lennon ran rampant on the right against Milan in last season’s Champions League encounter, and Arsenal’s twin wingers Gervinho and Alex Oxlade-Chamberlain continued to exploit that particular weakness in their 3-0 win at the Emirates this season.

Messi had no luck through the congested middle

All these Barcelona events occurred in the first half of the game, but that’s not to say it was a one-sided half. Just like most of Barcelona’s opponents, Milan looked to pressure Barcelona high up the pitch, early in the first half. But when Barcelona settled into their neat passing patterns in Milan’s half, Milan formed a narrow compact defensive unit (in response to Barcelona’s narrow attack) that on the whole, was comfortably effective.

Allegri’s team had some good chances in the first half; in fact, Milan’s chances were arguably better ones than Barcelona’s. It was early as the 2nd minute when Milan were presented with a golden opportunity to grab the lead, but Robinho produced a terrible effort on goal. It was a goalscoring chance that came from Milan’s high pressing, resulting in Busquets uncharacteristically giving the ball away to Seedorf near his own penalty box.

Another fantastic chance for Milan came in 19th minute, again as a result of Milan’s pressing. This time, Ambrosini dispossessed Xavi in Barcelona’s half and the loose ball fell to Seedorf. The ex-Real Madrid player then stroked a lovely pass through Pique and Puyol for Ibrahimovic, but the striker, so often accused of being a flat-track bully and not turning up on the big stages like the Champions League, couldn’t find the net against his former teammates as he shot tamely into Valdes’ arms.

Ambrosini’s performance in this match warrants a big mention, as he was easily Milan’s outstanding player of the night. There were those who feared for a Milan side shorn of Van Bommel, their usual midfield destroyer, but captain Ambrosini gave a fantastic display. He was Milan’s best defensive player with a brilliant contribution of 6 tackles and 6 interceptions, a count unmatched by his other teammates. Ambrosini was also the Milan player who committed the most fouls (5), but they were all smart, tactical fouls that helped to break up Barcelona’s metronomic passing rhythms. He did pick up a yellow card for an offence that wasn’t particularly yellow-card-worthy, but was possibly due to his consistent fouling.

Ambrosini: midfield general

Robinho’s display, however, was supremely disappointing. Playing on the left side of Milan’s attack, there was plenty of space behind Alves (who had advanced so far forward) for Robinho attack, but Robinho failed to capitalise on that tactical advantage. If his job wasn’t offensive in nature, but a defensive one to track Alves’ forward runs (unlikely, considering Robinho’s dislike for tracking back), he didn’t do that either.

In short, Robinho was by far Milan’s worst player: he offered little both offensively and defensively, blew a massive chance in the game’s opening stages, and when he went off injured for Stephan El Shaarawy in the 52nd minute, it seemed to be a boon rather than a bane for Milan.

On the rare occasions that Robinho or Ibrahimovic did try to attack down their left, it was Barcelona’s right-sided centre-back Mascherano who came rushing out to cover for Alves. Mascherano, like Ambrosini, had an excellent game as he always successfully nullified Milan’s sporadic threats down his side of defence. Mascherano made a whopping 7 tackles and 1 interception, illustrating his contribution to Barcelona’s clean sheet from this game.

The second half wasn’t filled with as many chances as the first, although Guardiola did try to shake things up in attack. Recognising that his team needed a lot more width, he withdrew Iniesta for winger Cristian Tello and later removed the ineffective Sanchez for another wide player Pedro Rodriguez.

Both wingers stationed themselves in wide positions, and Tello, reportedly a transfer target of Liverpool, had a few decent chances as he posed Milan’s defence with a new direction of attack, running directly at them from a wide berth. He also set Messi up for a shot (which was deflected for a corner) by pulling Antonini wide with him, and thus creating the room for Messi’s shot. Tello even forced Anotinini into yet another fist-pumping heroic sliding tackle after Abbiati had pushed Messi’s shot into Tello’s path.

Antonini with another goal-saving block

Tactically, Guardiola’s substitutions were spot-on, but the problem then was that at times, the midfield’s support was insufficient. While Barcelona initially looked too congested in the middle, their players looked too far apart from each other by the time Tello and Pedro came on. Xavi, who made quite a few good runs forward in the first half, didn’t make the same advances that was required of him in the second.

Perhaps it was due to Xavi tiring and being unaccustomed to playing at the tip of the midfield at such a high level match. If so, Guardiola should’ve then called on the services of Cesc Fabregas who was sitting on the bench, and was eventually an unused substitute. Fabregas is more than comfortable playing at the tip of a midfield three (it was in fact where he played during his time at Arsenal), and his direct forward runs from the centre would’ve been another handy weapon in breaking down Milan’s defence.

Another pertinent question is whether Keita should’ve played at all. While he didn’t do anything particularly wrong, he didn’t really add to Barcelona’s attack either. Guardiola seemed to have overestimated Milan’s attack: was there really a need for both Busquets and Keita in central midfield? With regards to Barcelona’s central midfield, would it have been a better option to play Xavi and Iniesta in their natural roles?

Milan didn’t create many chances (if at all), apart from a wasted opportunity as Urby Emanuelson, who came on in the 67th minute for the tiring Boateng, made a mess of his first touch of the ball when a good one would’ve sent him clear through on goal.

Allegri was then forced another massive blow when he had to take Nesta off after the centre-back picked up an injury, replacing him with Djamel Mesbah in the 75th minute. At that moment, there were real worries for Milan’s safety in the game as the gulf in quality between Nesta and Mesbah is undeniably huge, but Milan seemed determined to settle for a draw and saw the game out.

How the teams ended the game - Barca changed their shape to increase width

On the whole, both sides will probably feel that a 0-0 score is a fair one, but also feel that this match was an opportunity wasted, given that neither were at the top of their game.

Allegri will be pleased that his team were the first side in 30 Champions League away games to prevent Barcelona from scoring. His Milan side require a score draw and not a win at the Camp Nou – a feat they achieved this season in the group stages with a 2-2 draw – to progress to the semi-finals.

Milan will fancy their chances, but Allegri surely has to address his team’s poor conversion rate and ensure every player performs to his maximum ability; a repeat performance from Robinho and even Ibrahimovic will definitely not do.

Barcelona need a win, nothing less. Though Barcelona’s away form this season has been patchy, their results at home have still been terrific. Guardiola will be respectfully confident as usual, but he will also be aware of the need for additional width: he got his defensive tactics right, but perhaps not his offensive ones.